Conventionally, as a structure for steam turbines or gas turbines, there is an abradable seal ring which fulfills the role of a seal between the rotor and housing and an ACC seal structure equipped with ACC (active clearance control) functions, as disclosed in patent documents 1 and 2 below.
The ACC seal structure is a structure which automatically adjusts the gap between the abradable seal ring and a rotor or fins arranged on a rotor.